Patent application title: MOTOR ASSEMBLY

Abstract:

A motor assembly includes a motor, a force transmission structure
comprising a drive plate and a shaft, and a gear train connecting the
motor to the drive plate for transmitting rotation of the motor to the
drive plate. The drive plate has a mounting hole with at least three
sections interconnected with one another at a common area, the shaft has
a toothed portion with at least three teeth fittingly received in the
sections of the mounting hole of the drive plate such that the shaft is
rotated with the drive plate.

Claims:

1. A force transmission structure comprising: a drive plate having a
mounting hole and a shaft fitted to the mounting hole for rotation with
the drive plate, wherein the mounting hole has at least three sections
interconnected with one another at a common area, the shaft has a toothed
portion with at least three teeth fittingly received in the sections of
the mounting hole such that the shaft is fixed to rotate with the drive
plate.

2. The force transmission structure of claim 1, wherein the drive plate
comprises a body and a coupling formed at the center of the body, the
coupling is axially deeper than the body, the mounting hole being formed
in the coupling.

3. The force transmission structure of claim 2, wherein the coupling has
buffer holes respectively located between adjacent sections.

4. The force transmission structure of claim 3, wherein the drive plate
has a plurality of protrusions formed on a first side of the body and
configured to engage with a driving member such that the driving member
is able to drive the drive plate, the shaft further comprises a pinion
configured to drive a driven member.

5. The force transmission structure of claim 4, wherein the drive plate
further comprises a plurality of ribs formed at an opposite second side
of the body.

6. The force transmission structure of claim 1, wherein the mounting hole
and the toothed portion are Y-shaped.

7. The force transmission structure of claim 6, wherein the drive plate is
made of a plastics material.

8. A motor assembly comprising:a motor;a force transmission structure
comprising a drive plate and a shaft; anda gear train connecting the
motor to the drive plate for driving the drive plate;wherein the drive
plate has a mounting hole with at least three sections interconnected
with one another at a common area, the shaft has a toothed portion with
at least three teeth fittingly received in the sections of the mounting
hole of the drive plate such that the shaft is fixed to rotate with the
drive plate.

9. The motor assembly of claim 8, wherein the gear train comprises a worm
driven by the motor, a worm gear meshed with the worm, and a damper
attached to and rotatable with the worm gear, the drive plate being
driven by the worm gear through the damper.

10. The motor assembly of claim 9, wherein the worm comprises an inner
ring, an outer ring, and a plurality of ribs extending from the inner
ring to the outer ring, the damper being received in a space formed
between the inner ring and the outer ring and having a plurality of first
slots for fittingly receiving the ribs respectively.

11. The motor assembly of claim 9, wherein the drive plate comprises a
body and a plurality of protrusions formed at one side of the body, and
the damper has a plurality of second slots engaging with the protrusions
of the drive plate.

12. The motor assembly of claim 11, wherein the protrusions are V-shaped,
the width of the protrusions increasing gradually from the inner most
portion towards the outer most portion in a radial direction of the body.

13. The motor assembly of claim 11, wherein the drive plate further
comprises a coupling formed at the center of the body, the coupling
having a greater axial depth than the body, and the mounting hole being
formed in the coupling.

14. The motor assembly of claim 13, wherein the coupling has buffer holes
respectively located between adjacent sections of the mounting hole.

15. The motor assembly of claim 8, wherein the mounting hole and the
toothed portion of the shaft are Y-shaped.

16. The motor assembly of claim 9, wherein the drive plate is made of a
plastics material, and the damper is made of rubber.

17. The motor assembly of claim 8, wherein the shaft further comprises a
pinion for driving a gear of a window lift system.

18. The motor assembly of claim 8, wherein the shaft is held captive
within the mounting hole by a circlip located within a groove in the
distal end of the toothed portion.

[0002]This invention relates to a motor assembly, and in particular, to a
motor assembly having a force transmission structure.

BACKGROUND OF THE INVENTION

[0003]Usually, a window lift system for a vehicle window comprises a
driving motor, a lift device for moving up or down the glass of the
window, and a force transmission structure for transmitting rotation of
the output shaft of the motor to the lift device. The transmission
structure comprises a drive plate and a shaft coupled to the drive plate.
The drive plate is connected to the output shaft of the motor via a gear
train. The shaft is connected to the lift device via a pinion attached to
an end of the shaft and meshed with a gear of the lift device. In
operation, the motor drives the drive plate to rotate. The drive plate
drivingly rotates the shaft to thereby cause the lift device to move the
glass of the window up or down.

[0004]Conventionally, the shaft is coupled to the drive plate via a
cylindrical coupling end with two flat surfaces at opposite sides thereof
fittingly received in a waist-shaped hole of the drive plate. Two
opposite flat interfaces are formed between the coupling end of the shaft
and the hole of the drive plate. In operation, two reverse forces are
exerted on the two flat surfaces of the coupling end of the shaft, which
will generate impact on the shaft and the drive plate to thereby generate
vibration and noise.

[0005]As such, there is a desire for an improved transition structure
which can solve the above-mentioned problems.

SUMMARY OF THE INVENTION

[0006]Accordingly, in one aspect thereof, the present invention provides a
force transmission structure comprising: a drive plate having a mounting
hole and a shaft fitted to the mounting hole for rotation with the drive
plate, wherein the mounting hole has at least three sections
interconnected with one another at a common area, the shaft has a toothed
portion with at least three teeth fittingly received in the sections of
the mounting hole such that the shaft is fixed to rotate with the drive
plate.

[0007]Preferably, the drive plate comprises a body and a coupling formed
at the center of the body, the coupling is deeper than the body in the
axial direction of the body, the mounting hole being formed in the
coupling.

[0008]Preferably, the coupling has buffer holes respectively located
between adjacent sections.

[0009]Preferably, the drive plate has a plurality of protrusions formed on
a first side of the body and configured to engage with a driving member
such that the driving member is able to drive the drive plate, the shaft
further comprises a pinion configured to drive a driven member.

[0010]Preferably, the drive plate further comprises a plurality of ribs
formed at an opposite second side of the body.

[0011]Preferably, the mounting hole and the toothed portion are Y-shaped.

[0012]Preferably, the drive plate is made of a plastics material.

[0013]According to a second aspect, the present invention provides a motor
assembly comprising: a motor; a force transmission structure comprising a
drive plate and a shaft; and a gear train connecting the motor to the
drive plate for driving the drive plate; wherein the drive plate has a
mounting hole with at least three sections interconnected with one
another at a common area, the shaft has a toothed portion with at least
three teeth fittingly received in the sections of the mounting hole of
the drive plate such that the shaft is fixed to rotate with the drive
plate.

[0014]Preferably, the gear train comprises a worm driven by the motor, a
worm gear meshed with the worm, and a damper attached to and rotatable
with the worm gear, the drive plate being driven by the worm gear through
the damper.

[0015]Preferably, the worm comprises an inner ring, an outer ring, and a
plurality of ribs extending from the inner ring to the outer ring, the
damper being received in a space formed between the inner ring and the
outer ring and having a plurality of first slots for fittingly receiving
the ribs respectively.

[0016]Preferably, the drive plate comprises a body and a plurality of
protrusions formed at one side of the body, and the damper has a
plurality of second slots engaging with the protrusions of the drive
plate.

[0017]Preferably, the protrusions are V-shaped, the width of the
protrusions increasing gradually from the inner most portion towards the
outer most portion in a radial direction of the body.

[0018]Preferably, the drive plate further comprises a coupling formed at
the center of the body, the coupling having a greater axial depth than
the body, and the mounting hole being formed in the coupling.

[0019]Preferably, the coupling has buffer holes respectively located
between adjacent sections of the mounting hole.

[0020]Preferably, the mounting hole and the toothed portion of the shaft
are Y-shaped.

[0021]Preferably, the drive plate is made of a plastics material, and the
damper is made of rubber.

[0022]Preferably, the shaft further comprises a pinion for driving a gear
of a window lift system.

[0023]Preferably, the shaft is held captive within the mounting hole by a
circlip located within a groove in the distal end of the toothed portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]A preferred embodiment of the invention will now be described, by
way of example only, with reference to figures of the accompanying
drawings. In the figures, identical structures, elements or parts that
appear in more than one figure are generally labelled with a same
reference numeral in all the figures in which they appear. Dimensions of
components and features shown in the figures are generally chosen for
convenience and clarity of presentation and are not necessarily shown to
scale. The figures are listed below.

[0025]FIG. 1 is a partial cross sectional view of a motor assembly in
accordance with an embodiment of the present invention;

[0026]FIG. 2 is an exploded view of the motor assembly of FIG. 1;

[0027]FIG. 3 is a plan view of a drive plate of the motor assembly of FIG.
1;

[0028]FIG. 4 is an isometric view of a shaft of the motor assembly of FIG.
1;

[0029]FIG. 5 is an assembled view of the drive plate of FIG. 3 and the
shaft of FIG. 4; and

[0030]FIGS. 6A and 6B are schematic diagrams showing forces acting between
the drive plate and the shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031]FIG. 1 shows a partial cross sectional view of a motor assembly in
accordance with the preferred embodiment of the present invention. The
motor assembly comprises a motor 10 and a gear train driven by the motor
10. The gear train includes a force transmission structure. The gear
train is contained in a gear housing 14 and a capstan 16, which is a part
of a window lift mechanism, is visible at the back. The capstan is driven
through gears (not shown) by the motor assembly.

[0032]FIG. 2 is an exploded view of the gear train, with the gear housing
removed, to show the various components. The gear train comprises a worm
20 fitted to a motor shaft 12 driven by the motor 10, a worm gear 30
which meshes with the worm 20, a damper 40, a drive plate 50 and a shaft
60. The force transmission structure comprises the drive plate 50 and the
shaft 60. The worm 20 may be press fitted to the motor shaft 12.
Alternatively, the worm 20 may be formed integral with the motor shaft
12. The worm gear 30 comprises an inner ring 31, an outer ring 33, and a
plurality of ribs 32 radially extending from the inner ring to the outer
ring. Teeth are formed at the outer circumferential surface of the outer
ring 33, for meshing with the worm 20. The damper 40 is made of rubber
material, has a through opening at the center thereof and has a plurality
of first slots 41 and second slots 42 extending radially thereof. The
slots 41, 42 are arranged alternately in the circumferential direction.

[0033]Referring also to FIG. 3, the drive plate 50, which may be made of
an engineering plastics material, comprises a round body 52, a coupling
54 formed at the center of the body 52, a plurality of V-shaped
protrusions 56 formed on one side of the body 52, and a plurality of ribs
58 formed on the opposite side of the body 52. The coupling 54 extends
beyond the body 52 in opposite axial directions of the body 52 and
therefore the coupling 54 has a greater depth or thickness than the body
52. The coupling 54 has a Y-shaped mounting hole 55 at the center
thereof, that is, the mounting hole 55 comprises three sections
interconnected at the center thereof. Preferably, the coupling 54 further
has a plurality of buffer holes 57. In the embodiment, the buffer holes
57 are three blind holes which do not pass completely through the
coupling 54 axially, and are evenly distributed in the circumferential
direction, each one being located between adjacent sections of the
Y-shaped hole 55. In this embodiment, the protrusions 56 comprise three
protrusions 56 evenly distributed in the circumferential direction, the
width of the protrusions increasing gradually from the inner most portion
towards the outer most portion in the radial direction of the body 52.
The central line of each protrusion 56 extends radially through the
center of the body 52. The protrusions 56 are shaped and sized to fit the
second slots 42 of the damper 40.

[0034]Referring to FIG. 4, the shaft 60, which is the output shaft of the
gearbox in the preferred embodiment, comprises a round portion 61, a
toothed portion 62 formed at one end of the round portion, and a pinion
64 formed at the other end of the round portion. The toothed portion 62
has a Y-shaped cross section and comprises three teeth evenly distributed
in a circumferential direction of the shaft 60. The shape and size of the
teeth of the toothed portion 62 conform to that of the mounting hole 55
of the drive plate 50. Preferably, the shaft 60 is made of low alloy
steel. Alternatively, the shaft 60 may be made of other metal material.
The pinion 64 is configured to couple with a gear, such as a gear train
of a lift mechanism of a window lift system.

[0035]Referring to FIGS. 1 and 5, when assembled, the damper 40 is located
in a spaced formed between the inner ring 31 and outer ring 33 of the
worm 30 and the ribs 32 of the worm 30 are received in the first slots 41
of the damper 40. The protrusions 56 of the drive plate 50 are
respectively, interferentially and fittingly received in the second slots
42 of the damper 40. Thus, the drive plate 50 is rotated by the damper 40
and the worm gear 30 when the worm 20 drives the worm gear 30.

[0036]The Y-shaped toothed portion 62 of the shaft 60 extends through the
inner ring 31 of the worm gear 30 to be fitted in the Y-shaped mounting
hole 55 of the drive plate 50. The free end of the toothed portion 62 of
the shaft 60 extends beyond the coupling 54. A circlip 70 is fitted in a
slot 66 formed at the free end of the toothed portion 62 to prevent the
toothed portion 62 escaping from the mounting hole 55. In operation, the
motor 10 rotates the motor shaft 12, which rotates the worm 20, which
drives the worm gear 30, which rotates the drive plate 50 via the damper
40, and thus rotates the shaft 60. The drive plate 50 drives the shaft 60
to rotate by the Y-shaped mounting hole 55 of the drive plate mating with
the Y-shaped toothed portion 62 of the shaft 60. Consequently, the pinion
64 drives the capstan 16 via one or more gears (not shown) of the window
lift system to thereby raise up or lower down the glass of the window.
The window lift system may have a wire which is wound about the capstan
to raise or lower the glass

[0037]Referring to FIGS. 6A and 6B, in the embodiment of the present
invention, when the shaft 60 is rotated by the drive plate 50, three
equal forces A, B, C from the coupling 54 are exerted on the three teeth
of the toothed portion 62 of the shaft 60 respectively. These three
forces A, B, C exerting on the three teeth of the toothed portion 62
constitute a triangle as shown in FIG. 6B. Therefore, the shaft 60 is
rotated stably to thereby move up and/or down the glass of the window
lift system quietly. Furthermore, the contact area between the teeth of
the shaft 60 and the coupling 54 of the drive plate 50 is greater than
that in the traditional design, which results in the connection between
coupler and the shaft being able to withstand a greater torque. Moreover,
the drive plate 50 is ideally made of an engineering plastics material
which has good strength and resistance to impact and can absorb
vibration, which is helpful to reduce the noise generated by the gear
train as well. The buffer holes 57 aid molding of the drive plate by
providing relief when the plastics material is cooling in the mould to
reduce distortion of the mounting hole 55.

[0038]In the description and claims of the present application, each of
the verbs "comprise", "include", "contain" and "have", and variations
thereof, are used in an inclusive sense, to specify the presence of the
stated item but not to exclude the presence of additional items.

[0039]Although the invention is described with reference to one or more
preferred embodiments, it should be appreciated by those skilled in the
art that various modifications are possible. Therefore, the scope of the
invention is to be determined by reference to the claims that follow.